Ubuntu :: HDD Crashed After Installing 10.04?

I have 2 hard disks installed in my system, 160 GB and 500 GB. I have using windows 7 installed on the 160 GB disk for past 2 years now and never faced any problem with my HDDs. Now this 500 GB is some problematic one. Remember the 500 gb disks from seagate which was a huge failure, i have that model. I bought it with 3 more of my friends. All other's HDD's crashed again and again except mine. I did some scanning and all with all sort of HDD softwares but all is well, except one soft called HDD health that showed my 500 gb has 48% health. It remain like that for an year, so i stopped worrying about that. I have stuffed my disk with data and never faced any problem up untill now. Now yesterday i decided to install Ultimate edition 2.7 64-bit. I downloaded it and burned the dvd at 4x speed and how i wanted to install it is like the way that it should go into the 500 gb one without having to do anything with 160 gb one having windows 7. I have done this earlier and it caused absolutely no problem. I just change the boot sequence to whatever disk i wanted to log into windows or linux(remember i did that with the same disks). Now i emptied a partition in 500 gb one, deleted it with the help of partition manager inbuild in windows 7, unplugged the 160 gb and booted thru live cd of UEU 2.7 and started the installation. When i got on the partition selection screen, what it showed me was just a 500 gb of "unallocated space", which i s actually healthy 6 partitions containing data which i have been using for years. No traces of the 30 space i unallocated in windows for linux. Now first question, "Why the hell did it not recognized my HDD when its perfectly operational in windows and i have installed UEU 2.5 on it once". It should have shown me the partitions. Does that means that my HDD was having some problem already ?? Now i booted back in windows, reallocated my 30 gb space, emptied some space from a 160 gb HDD's partition and got back into linux, with both HDD's plugged in this time. Now i started the installation. Again it didnt recognized the 500 gb chunk but did recognized the partitions in 160 gb and also recognized windows 7 installation. I formatted the partition with ext 4, didnt provide any partition for swap as i have 4gb ram and changed the boot loader to GRUB. Installation was successful. I can see all the drives from 160 GB one but only one partition from 500 GB one, no traces of other partitions, not even in Gparted. And yeah, the disk was mounted. Now everything was looking fine, i switched back and forth from windows to linux a couple of times, switched off the computer for some time, switched back on and watched a movie and finally shut down properly last night.

Now this morning my brother switched on the PC and it just wonts start. It restarts again and again just after the BIOS screen. I checked everything but couldnt find the problem. So finally i de attached the hardware one by one and found its the 500 GB that was causing the problem. I plugged it out and booted in again. To my surprise, the windows 7 booted in from 160 GB HDD with no traces of linux what so ever. Its was in the same HDD, i installed the common boot loader and have seen it my self when i switch on the pc, showing all linux options first and then windows 7 as other OS. It has nothing to do with 500 GB one, no dynamic partition, no system files or any thing. I suppose that windows 7 cant take back te boot loader without the help of installation disk and i have not used any. There was not even any kind of system recovery installed. Then how the hell windows 7 came back and linux just disappeared. The partition manager shows that the newly created partition for linux as "healthy and primary" partition.

say it once that all this mess was only due to i screw up the installation and my 500 GB is not dead. I will die without my data.